Radio noise-free switch



Sept. 17, 1968 R. J. COBURN RADIO NOISE-FREE swrrcn Original Filed Sept.28, 1962 INVENTOR. RICHARD J. COBURN ATTORNEYS United States Patent3,402,302 RADIO NOISE-FREE SWITCH Richard J. Coburn, West Hartford,Conn., assignor to Dynamic Controls Corporation, South Windsor, Conn., acorporation of Connecticut Original application Sept. 28, 1962, Ser. No.226,825, now Patent No. 3,237,030, dated Feb. 22, 1966. Divided and thisapplication Feb. 1, 1966, Ser. No. 524,349

1 Claim. (Cl. 307133) ABSTRACT OF THE DISCLOSURE A switch comprisingfirst and second oppositely oriented controlled rectifiers in a powerline each with a control circuit comprising a controlled rectifier and atransistor adapted to cause the power line rectifiers to conductinitially at substantially zero potential, and an arming switch.

This invention relates to electrical switches and has as its generalobject the provision of a switch usable in a power line between a sourceof energy of varying potential and a load and which may be closed andopened under comparatively heavy power loads and will yet generatesubstantially no radio noise.

This application is a division of my copending application, Serial No.226,825, filed September 28, 1962, now Patent No. 3,237,030, RadioNoise-Free Switch.

A further object of the invention resides in the provision of a switchof the type referred to and which includes a main switching means and anauxiliary switch ing means, the latter being adapted to close and openrespectively before and after closing and opening of the former and atcomparatively low voltage conditions whereby to substantially eliminateradio noise.

A still further object of the invention resides in the provision of aswitch of the type mentioned wherein the main switching means is of themechanical type and wherein the life of the contacts thereof issubstantially increased by the operation of the auxiliary switchingmeans.

Still another object of the invention is to provide a switch of the typementioned and which exhibits characteristics of comparatively low powerloss.

The drawing shows a preferred embodiment of the invention and suchembodiment will be described, but it will be understood that variouschanges may be made from the construction disclosed, and that thedrawing and description are not to be construed as defining or limitingthe scope of the invention, the claim forming a part of thisspecification being relied upon for that purpose.

The single figure of the drawing is a schematic illustration of a switchembodying the present invention and which is incorporated in a powerline between a generator and a load.

Referring now particularly to the drawing, it will be observed that apower line extends between a source of electrical energy of varyingvoltage 12 and a load 14. The electrical energy source 12 is shown ascomprising an alternating curernt generator but the switch of thepresent invention is equally adaptable for use with other sources ofvarying potential both DC and AC. Similarly, the character of the load14 may vary widely within the scope of the invention.

The switch of the present invention is identified generally by thereference numeral 16 and a first portion thereof comprises a mainswitching means 18. The main switching means 18 may vary in form but isshown as being of the mechanical type and comprising a switching memberor arm 20 and an associated contact 22. The

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switching member or arm 20 is movable in one and an opposite directionfor opening and closing operation and, more specifically, upwardswinging movement thereof to the position shown effects openingoperation and downward swinging movement to engagement with the contact22 effects closing operation.

In accordance with the invention the switch 16 also includes anauxiliary switching means indicated generally at 24 and which isconnected with the power line 10 in parallel with the first or mainswitching means 18. The auxiliary switching means 24 may vary in formbut in accordance with the presently preferred practice and where analternating current supply 12 is involved, the said means comprisesfirst and second oppositely oriented unidirectional conducting elements26 and 28. More particularly, the elements 26 and 28 take the form ofSilicone Controlled Rectifiers having gate terminals 30, 32, anodeterminals 34, 36 and cathode terminals 38 and 40. The controlledrectifier 26 has its anode and cathode terminals 34 and 38 connected ina line 42 extending between first and second branch lines 44, 46connected with the power line 10 respectively on the generator and loadside of the first or main switching means 18. The controlled rectifier28 has its anode and cathode terminals 36, 40 connected in a line 48which also extends between said branch lines 44 and 46. As will be seenthe rectifier 26 is arranged in the line 42 to conduct when the voltageon the load side of the switching means 18 is positive with respect tothe voltage on the generator side of said switching means. Conversely,the rectifier 28 is arranged to conduct when the voltage on thegenerator side of said power line is positive with respect to thevoltage on the load side thereof.

Further in accord with the invention, the switch 16 includes a controland operating circuit means connected with the power line 10 and withthe main and auxiliary switching means 18 and 24. Said operating andcontrol circuit means may vary widely in form but as shown comprises aselectively operable means 50 for opening and closing the main switchingmeans 18, a selectively operable actuating means 52 and first and secondgate supply circuits 54 and 56. The selectively operable means 50 foroperating the main switching means 18 is shown as comprising anelectrical force generating means in the form of a relay coil 58connected in a line 60 and provided with a local ground 62. The line 60extends to a contact 64 associated with a switch member 66 which, inturn, is connected with an electrical energy source 68 in the form of abattery grounded locally at 70. Thus, the switch member 66 can be movedto a closed position whereby to energize the relay coil 58 and to closethe switching member or arm 20 in the usual manner. Deenergization ofthe relay coil 58 on opening movement of the switch member 66 willresult in opening movement of the switching member 20 to the positionshown.

The selectively operable actuating means 52 may vary in form but isshown as comprising first and second switch members 72 and 74 connectedfor gang operation with the switch member 66. The switch member 72 hasan associated contact 76 in a line 78 extending to a control circuitmeans including the gate supply circuit 54. Opposite the contact 76 theswitch member 72 is connected with the power line 10 on the generatorside of the main switching means 18 through an electrical energy sourcein the form of a battery 80 and by means of a line 82.

The switch member 74 has an associated contact 82 in a line 84 connectedwith the power line 10 on the load side of the main switching means 18.An energy source in the form of a battery 83 is disposed in the saidline 84. The opposite side of the switch member 74 is connected with aline 86 extending to the control means including the gate supply circuit56.

Referring now to the gate supply circuit 54, it will be observed thatthe line 78 extends to a resistor 88 and thence to a control switchingmeans 90 and the aforementioned gate terminal 30 of the controlledrectifier 26. The control switching means 90 preferably comprises acontrolled rectifier as shown with an anode terminal 92, a cathodeterminal 94 and a gate terminal 96. The controlled rectifier 90 isoriented in the line 78 to conduct from the switch member 72 to the gateterminal 30 of the rectifier 26 when the potential at said switch memberis positive with respect to the potential at said gate terminal.

The gate supply circuit 54 also includes a line voltage responsive meanswhich is operable to effectively open and close the control switchingmeans or rectifier 90. Said line voltage responsive means comprises atransistor 98 having a base terminal 100, a collector terminal 102 andan emitter terminal 104. The base terminal 100 is connected through aresistor 106 with the aforementioned branch line 46 by means of a line108. The collector terminal 102 is connected with the gate 96 of thecontrolled rectifier 90 by a line 110 and with the aforementioned line78 by means of a line 112 extending between the line 78 and the line110. A resistor 114 is connected in the line 112. The emitter terminal104 of the transistor 98 is connected with the aforementioned branchline 44 by means of a line 116 and a line 118 extends from the line 116to the line 78. Disposed in the line 118 is a capacitor 120.

Referring now to the gate supply circuit 56, it will be observed thatthe said circuit is substantially identical with the circuit 54 but in areverse arrangement. The aforementioned line 86 from the switch member74 extends to a resistor 122, a controlled rectifier 124 having anodeand cathode terminals 126 and 128 and a gate tenminal 130 and thence tothe gate terminal 32 of the rectifier 28. The controlled rectifier 124constitutes a control switching means as in the case of the rectifier90. Associated with the said control switching means is a line voltageresponsive means comprising a transistor 132. The transistor 132 has abase terminal 134, a collector terminal 136 and an emitter terminal 138.The base 134 of the transistor is connected through a resistor 140 withthe aforementioned branch line 44 by means of a line 142. The collector136 of the transistor is connected with the gate terminal 130 of thecontrolled rectifier 124 by means of a. line 144. Extending from saidline 144 to the line 86 is a line 146 which has disposed therein aresistor 148. The emitter terminal 138 of the transistor 132 isconnected with the aforementioned branch line 46 by means of a line 150.Extending between the line 150 and the line 86 is a line 152 anddisposed therein is a capacitor 154.

OPERATION In operation of the switch 16 as shown, the switch members 72,66 and 74 may be opened or closed simultaneously. Generally speaking, itwill be observed that closing of the switch members 72, 66 and 74 willresult in closing of the main switching means 18. Prior to closing ofthe said main switching means however, the controlled rectifiers 26 and28 of the auxiliary switching means 24 will be closed or renderedconductive and, moreover, such closing of the auxiliary switching meanswill occur when the power line voltage is substantially below peak linevoltage. More specifically, the auxiliary switching means is closed, orit may be said that the controlled rectifiers commence conducting, whenpower line voltage is substantially below 50% of the peak line voltageand, in fact, very near zero potential. Thus, the rate of current changeat the instant when the auxiliary switching means starts to conduct willbe as low as possible, the resulting fields generated will be of lowmagnitude, and little or no radio noise will be encountered. Onsubsequent closing of the main switching member 20, current will alreadybe flowing through the power line 4, 19, the branch lines 44 and 46 andthe lines 42 and 48 and an excessive rate of change of current flow willnot be encountered at the main switching means 18. Thus, little or noradio noise will be encountered on closing of the main switching means.In accordance with the invention the electrical resistancecharacteristics of the main switching means 18 is substantially lowerthan the corresponding characteristic of the auxiliary switching means24. Thus, substantially all of the current will flow through the mainswitching mean-s after the same has been closed.

In generally describing the opening operation of the switch 16, itshould be noted that the capacitors and 154 provide a time delayfunction whereby the auxiliary switching means 24 opens after theopening of the main switching means 18. On opening of the switch members72, 66 and 74, the switching member 20 opens with the generation oflittle or no radio noise and without arcing due to the continued flow ofcurrent through the branch lines 44, 46, the lines 42 and 48 and thecontrol rectifiers 26 and 22. Thereafter, and as will be seen, a gateopening signal is removed from the gate terminals 30 and 3-2 of therectifiers 26 and 28, and the said rectifiers serve automatically toopen or cease conducting at Very low voltage levels substantially belowpeak power line voltage and, in fact, substantially at zero potential.As is well known, controlled rectifiers such as Silicone ControlledRectifiers have an inherent characteristic of be coming nonconductive inthe absence of a gate opening signal or voltage on interruption of theiranode current. Thus, closing of the auxiliary switching means occurssubstantially at zero potential and little or no radio noise isgenerated.

Considering the operation of the switch 16 in greater r detail andreferring to a closing operation in particular,

assume that the power line voltage 10 is substantially at a positivepeak when the switch members 72, 66 and 74 are closed. As mentionedabove, relay coil 58 will be energized to close the switching member 20but closing of the auxiliary switching means 24 will occur prior toengagement of the said switching member With the contact 22. The closedswitch member 72 provides a positive voltage signal through the line 78to the control switching means or controlled rectifier 90. Additionally,a positive voltage signal is applied to the gate terminal 96 of thecontrolled rectifier 90 by means of the lines 112 and 110, thetransistor 98 being nonconductive due to the presence of a potential atits emitter terminal 104 which is positive with respect to the potentialat its base terminal 100. A positive voltage signal to the gate 96serves to open the gate and thereby to close or render the controlledrectifier 90 conductive in the forward direction. Thus, the gateterminal 30' of the controlled rectifier 26 is provided with a positivevoltage signal whereby to open said gate and to close or renderconductive the rectifier 26. Said controlled rectifier 26, however, isnot instanteously effective to conduct current as it will be noted thatthe potential thereacross is in the rearward direction, i.e., branchline 44 is more positive than branch line 46.

Referring now to closing of the switch member 74, it will be observedthat a positive potential is applied to the controlled rectifier 124 atits anode terminal 126 and to the gate of said rectifier through thelines 146 and 144. With the line voltage at or substantially at positivepeak, however, the voltage at the base terminal 134 of the transistor132 will be positive with respect to the voltage at the emitter terminal128 of said transistor. Thus, the transistor 132 will be renderedconductive and will maintain the gate 130 closed despite the positivesignal in the line 86 from the battery 83. The gate terminal 32 of therectifier 28 will not receive a positive signal necessary for opening ofsaid gate and the said rectifier 28 will remain closed or nonconductivefor the duration of the high power line voltage.

Still referring to the gate supply circuit 56 and the rectifier 28, itis to be noted that the transistor 132 will cease conducting as thepower line voltage moves downwardly on its sine curve and is reducedfrom its peak value. More specifically, at a very low positive voltage,the transistor 132 will cease conducting and the necessary positivevoltage signal will be applied to the gate 130 whereby to open the sameand to render the rectifier 124 conductive. This results in theapplication of a positive voltage signal to the gate terminal 32 of thecontrolled rectifier 28 and the opening of said gate. Opening of thegate of the rectifier 28 results in closing or a conductive condition ofthe said rectifier. At this instant in time, the line voltage being at avery low positive value, the rectifier will begin to conduct a currentflow from the branch line 44 through the line 48 to the branch line 46and the auxiliary switching means 24 may be regarded as closed. When theline voltage follows its sine curve to the negative side, the rectifier26 will commence conducting in a similar manner and current flow throughthe auxiliary switch means 24 will have commenced with little or noradio noise and will pro vide for closing of the switching member 20with little or no radio noise.

Now from the foregoing it will be apparent that the operating andcontrol circuit means of the present invention provides for closing ofthe rectifiers 26 and 28 when the potential thereacross is in a rangeextending between low forward potentials and through the rearwardpotentials. There can be of course be no excessive rate of change ofcurrent flow when the rectifiers are subjected to rearward potentialsand it is therefore possible only to close the auxiliary switching means24 at very low voltages with the benefit of substantial elimination ofradio noise. In the embodiment of the invention shown, the variouselements are selected to provide for closing of the controlledrectifiers 26 and 28 at approximately 1 volts. This provision is made ina power line system wherein the peak power line voltages are on theorder of 160 volts. Thus, closing of the auxiliary switching means 24may be said to occur substantially at zero potential, the said potentialbeing low enough to substantially eliminate radio noise.

Referring now to the opening operation of the switch 16 in greaterdetail, it will be observed that the capacitors 120 and 152 are arrangedso as to be charged when the switch is in the closed condition. Onopening of the switch members 72, 66 and 74, the relay coil 58 isde-energized and the switching member 20 opens. During this period oftime, the capacitors 120 and 152 discharge to the lines 118 and 78 andthe lines 152V and 86 respectively whereby to provide the necessarypotential for maintaining the gate supply circuits 54' and 56 inoperation and for maintaining the rectifiers 26 and 28 in closedcondition. When the capacitors 120 and 152 are discharged so as to nolonger provide gate signals for the rectifiers 26 and 28 the saidrectifiers automatically open or become unconductive at very lowvoltages and substantially at zero potential in accord with theirinherent characteristics mentioned above. In the embodiment of theinvention shown, said voltages may be on the order of 1 /2 volts and,little or no radio noise is generated in opening of the main switchingmeans 18 and in opening of the auxiliary switching means 24.

The resistors 106 and 140 have not been defined as to functionheretofore and it should be noted that the said elements serve to reducevoltage to an appropriate level respectively for the transistors 98 and132. Resistors 114 and 88 serve as current limiters for the transistor98 and the controlled rectifier Resistors 122 and 148 similarly serve ascurrent limiters for the controlled rectifier 124 and the transistor132.

Finally, it is to be observed that the switch 16 has additionaladvantages over elimination of radio noise. As mentioned, the resistancerelationship of the main and auxiliary switching means is such that themain switching means has substantially lower resistance than theauxiliary switching means. This provides for a condition whereinsubstantially all current flow occurs through the main switching meansonce the switch is closed. Thus, the Silicone Controlled Rectifiers 26and 28, comparatively expensive elements, may *be utilized in very smallsize as compared with switches wherein such elements comprise the mainswitching and current carrying means. Substantially lower costs areencountered in the provision of such small rectifiers.

Power losses in the switch are desirably low as compared with a switchwherein Silicone Controlled Rectidiers are employed as the principalswitching and current carrying members. The main switching means 18 maybe of a conventional mechanical type affording characteristics ofextremely low power loss.

Still further, engagement of the switching member 20 with the contact 22in the main switching means 18 should be noted as occurring only whenthe auxiliary switching means is first closed as stated. It is foundthat a substantial reduction in contact wear is thus achieved and anextremely long life of the contacts in the main switching means is to beexpected.

The invention claimed is:

1. A switch for use in a power line between a source of AC electricalenergy and a load, said switch comprising first and second oppositelyoriented controlled rectifiers each having anode and cathode terminalsconnected with said power line and each also-having a gate terminal,power line voltage responsive control circuit means connected with saidpower line and said gate terminals and serving to render said rectifiersoperable to conduct initially when power line voltage is atsubstantially zero potential, said means comprising first and secondgate supply circuit connected respectively with said gates and eachincluding a controlled rectifier and a transistor connected in circuitwith the former and operating the same, and selectively operableactuating means connected with and adapted to arm control circuit meansfor its aforesaid operation.

References Cited UNITED STATES PATENTS 3,237,030 2/1966 Coburn 307-2,441,789 5/ 1948- Bivens.

2,789,253 4/ 1957 Vang.

3,204,113 8/ 1965 Snygg 307-885 3,259,825 7/ 1966 James.

ROBERT K. SCHAEFER, Primary Examiner. T. B. JOIKE, Assistant Examiner.

